Granular body and method of making same



p 1931- R. SEABURY 1,824,795

GRANULAR BODY AND METHOD OF MAKING SAME Filed July 5, 1926 PatentedSept. 29, 1931 UNITED STATES PATENT OFFICE.

RALPH L. SEABURY OF TOLEDO, OHIO, ASSIGNOR TO DELCO-REMY CORPORATION, OFANDERSON, INDIANA, A CORPORATION OF DELAWARE GRANULAR BODY AND METHOD OFMAKING SAME Application filed July 3, 1926. Serial No. 120,540. 2

This invention relates to compressed granular bodies adapted to be usedas bearings, electrical conductors, such for instance as electricbrushes, and for other purposes,

. and to a method of making same.

The invention consists broadly in electroplating the granular body,after molding the same into preliminary shape and baking it in suchshape, and then compressing the electroplated body in a die under aconsiderable pressure to re-arrange the internal structure of the body,to force the electroplating into more intimate contact with theparticles composing the body and make the plating less porous, and atthe same time imparting the exact shape and size desired to the body.

Another advantage resulting from compressing the electroplated body in adie is obtained by the burnishing, smoothing or polishing action whichtakes place by reason of the frictional engagement of the sides of thebody with the die when the body is forced therefrom. Such automaticburnishing of the article saves an extra operation forsuch purpose, andin the case of an electric brush or other electrical conductor combineswith the compressing action to give the article a better electricalcontacting surface.

Other and further advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, wherein preferred embodiments of the present invention areclearly shown.

In the drawings: .Fig. 1 is a sectional view taken on the line 1-1 ofFig. 2.

Fig. 2 is a sectional view taken on the line 2--2 of Fig. 1 showing thebrush in position immediately before being compressed.

Fig. 3 is a sectional view similar to Fig. 1. showing the brushimmediately after being compressed.

Fig. 4 shows the finished brush being ejectedfrom the die.

Fig. 5 shows a perspective view of the finished brush. v

In the preferred and practical operation of my process in themanufacture of electric brushes, I employ a mixture composedsubstantially of 80% powdered or finely cut copper, 12% powdered lead,and 8% powdered graphite. These materials may be of various degrees offineness, but I find that the best results are obtained by usingmaterials Which would pass through a 100 mesh screen. These powders areintimately mixed together and are then compressed under pressure ofabout 15 tons per square inch in a die or mold, not shown, suitablyshaped to form the brush 1O somewhat larger than the final finishedsize, but a little narrower than the desired final width. By using theproper'amount of material in this molding operation, the brush so formedwill have a width V and thickness 'l slightly smaller than the desiredfinal widthand thickness but a length L appreciably longer than thefinal desired length. The brush thus formed is heated to a temperatureof about 750 0., which causes a metalization or partial coalescence ofthe particles composing the brush, thereby imparting a. distinctlymetallic character to the brush so much so that it can be hammered ordeiormed by pressure Without disrupting its structure, providing thedeformation has not been excessive. The heating, however, should not besuch as to cause a general fusing together of the material forming thebrush.

After the baking operation the brush is electro lated and then subjectedto a pressure 0 about 15 tons per square inch in a die 14,.the size ofthe aperture 12 of the die 14 corresponding with the desired finishedwidth 'W;, and thickness T of the brush, the die being deep enough sothat the brush may be pressed from the ends. While it is pref? erable toelectroplate the article after baking, these operations may bereversed,'if desired. Therefore, where baking and electroplating iscalled for by the claims, either operation may be first.

Theram16 is provided with a beveled surface 20 so as to provide aninclined surface 22 of the brush 10. The inclined surface 22 of thebrush 10 permits the brush to be placed at a slight angle when mountedon the motor as is well known to those skilled in the art.

- After the brush has'been re-shaped as dis- 5. repressingief the.article causes "shortening closed in Fig. 3 ram, 16 moves outwardly fromthe aperture in the die 14 to the positiondisclosed in Fig. 4 and theram 18 may move through the aperture 12, or the die 14 may move to righttothe position disclosed the reshaped brush 1 in very tight contact withthe walls of the. dieeven afterthepressure has been removed. Whenthepiece is ejected from the mold,

whichrequires anfappreciable pressure, due

' tolthe tightfitting of one within theother, the copper :platingisburnished or polished byJits frictional coaction with the die wall andacquires a highmetallic luster. The

brush is now'ready for use, although it is often desirablelto .grind theend which fits the commutatorin order to remove the copper platingat-that point. I

x The manufacture of electric-brushes and other electrical conductors inthis manner provides a smooth compressed metallic surfacethere'for,which makes a goodelectrical connection with holders or devices withwhich ibrought into contact and also gives the articles a pleasing andlfinished appear: ance. I 1

'Inthe practicing o'fmy metho'dzin connection withthe manufacture ofself-lubricated bearings, I preferably use a composition of copperpowder "82%, tin powder19%, lead powder 3% andgraphite powder.6%. Theseingredients afterbeing. thoroughly mixed are subjecte'dto -a pressure ofapproximately .20

tons per square inch'in a mold wherein the materialrisgiven aninitial-shape, which is preferablythat or ahollow cylinder. The moldedarticleis then-subject to a baking actio nthe samefas'described inconnection withfthe manufacture o'f'the electric brush,'andafterthefbaking the. article is electroplated to give it a surface.coating, preferably of'copper or br-ass. Thishavin'g been done, thearticle isimmersed inf lubricating oil,,of a which it'willabsorb a veryappreciable quantity. Theplated-and: impregnated, articleis then.repr'essediin a'finishing die, preferably using about 20 tons persquare inch-. The

mold for the original. forming of the article dimension of therrepressing die, while the inside dimension should beslightly larger,

baked -piece :into the i repressing die The The elecshould be r.slightly. smaller. than the outside 7 and further compression thereof,thereby resulting in an increase of density and hard ness, and alsocauses themetallic plating to be brought into more intimate contactwiththe particles composing the article and the plating itself is renderedharder and more durable. During the ejection of the'piece from therepressing die the plated surface acquires'a metallic luster andsmoothness.

The -re pressing,:after the oil impregnating" -operat1on,-causes theOlltO be more firmly held within the pores of the bearing than when itisrt reated with oil after the repressing or final shaping operation.This is, no doubt, dueto the fact that the repressingoperation serves toimprison or partially seal the oil within the pores of the. material.

, While the oil impregnating step is particularly desirable .inconnection with the manufacture of-bearin gs it isrsometimes usedanddesirable in connection with electric brushes "and-other articles. 7

When electroplating the inside or the bearing surface of the piece. itis desirable to use a brass plating in order to secure a lowercoefficient of friction. Thepressing-o-f this plating givesthe article ahard, glossy wearing surface which atthe sametime is sufficiently porousto permitia fslight seepage of oil fromthe body of the bearingthroughthe plated surface. In this way thereissecured a ,goodlubricatingeffect. Whenfmade in this 1nanner,themain body of the bearingcan be composed ofless expensivematerials,

such as mixtures-ofgraphite and iron powders.- A mixture of iron with10% graphite can-be molded and treated similar to the treatmentstated-abovefor the copper graphite composition. Such a compositionwould be sutficiently porous forthe absorption of oil-while abrass-orbronze electroplatmg OIltllOlIlSlClQ surface would serve asthe bearlngsurface and. the lubricant could seep through thethin and-somewhatporous plat- While the form ofenibodiment of the present invention asherein disclosed, z constitutes a preferred form,-it=is to beunderstoodthat other forms might be adopted, all coming within the scopeofthe claims whichfollow. llfaving thus described my inventiomwhat' Iclaim asnew and desire to secure byLet-y the body under considerablepressureat both ends, while it is held in av die, to compact thematerial of the body andof the electroplat-j; VI

ing, and to provide a more intimate connection between the two.

2. The method of making a granular electrical conductor, consisting ininitially shaping under pressure the materials forming the article, theinitial shape having a smaller cross sectional area than the finalshape, then baking and electroplating the article, and then subjectingthe electroplated article to a compressing and re-shaping pressure in adie to give the article its finished form.

3. The method of providing a granular body with a metallic coating,consisting in forming the body with a smaller cross sectional area thanits final form, then electroplating the body and then subjecting it in adie to a compressing pressure at both ends which compacts both theinternal structure of the body and the coating, and causing the body tohave a frictional ejecting coaction with the die walls to burni h thecompacted coating.

In testimony whereof I have hereunto signed my name to thisspecification.

RALPH L. SEABURY.

